fix(quic): exclude locally rejected datagrams [CI]

backend/shared/MoShiro.Measurement/Net/MsQuicConnection.cs

@@ -99,7 +99,7 @@ internal sealed class MsQuicConnection : IAsyncDisposable, IDatagramConnection
         return RemoteEndPoint;
     }
 
-    public bool IsReady => _connected.Task.IsCompletedSuccessfully && Volatile.Read(ref _sendEnabled) != 0;
+    public bool IsReady => Volatile.Read(ref _handle) != 0 && _connected.Task.IsCompletedSuccessfully && Volatile.Read(ref _sendEnabled) != 0;
 
     public int MaxDatagramBytes => Volatile.Read(ref _maxDatagramBytes);
 

backend/shared/MoShiro.Measurement/Net/QuicDatagramTransport.cs

@@ -128,13 +128,16 @@ public sealed class QuicDatagramTransport : IDisposable, IAsyncDisposable
     public void Unregister(uint streamId) => _router.Unregister(streamId);
 
     /// <summary>Sends one measurement datagram on the connection for the supplied session.</summary>
-    public void Send(DataSession session, EndPoint target, ReadOnlySpan<byte> packet)
+    public bool Send(DataSession session, EndPoint target, ReadOnlySpan<byte> packet)
     {
         _ = target; // A QUIC connection owns its path; the Agent learns it from authenticated datagrams.
         if (session.DatagramConnection?.Send(packet) == true)
         {
             _router.Counters.PacketOut();
+            return true;
         }
+
+        return false;
     }
 
     public async Task RunAsync(CancellationToken ct)